This invention relates to semiautomatic pneumatic guns. More specifically, the invention is related to pneumatic guns having hammer assemblies for firing projectiles such as pellets, BBs, or paintballs.
Pneumatic guns are popular for firing various projectiles, such as pellets, BB""s, and frangible paint-filled balls known as xe2x80x9cpaintballsxe2x80x9d. In firing pneumatic guns, the user pulls a trigger to initiate a sequence of operation of components that results in the release of compressed gas that propels the projectile from the gun. The firing process in guns also continues with recocking the gun, so that it is again ready to fire. Loading of the next projectile in succession to be fired is considered to be a part of the recocking process.
Of particular interest to me are semiautomatic guns of the type that utilize a normally-closed, impact-openable gas regulating valve and a hammer. More particularly, I am interested in pneumatic guns of the type having a hammer that serves the dual functions of (1) impacting a valve actuator to open the valve and thus release compressed gas to fire the gun, and (2) responding to the urging of some of the released compressed gas to recock the gun. Typically in a gun of this type, when the gun is ready to fire, the hammer is restrained in the cocked position, rearward in the gun, by a trigger-actuated sear. When the user pulls the trigger to initiate firing, the sear moves and releases the hammer. Then, the hammer moves forward to the firing, valve-impact position. The normally-closed valve restrains compressed gas within a gas reservoir until the valve is opened briefly by the impact of the hammer moving forward under spring urging toward the valve. A portion of the released gas travels through a propulsion gas passageway to meet the rear of a projectile then in the gun firing chamber. The projectile is propelled forward and out through the barrel of the gun. Another portion of the released gas provides the motive force to return the hammer and associated gun parts back to the cocked position, thereby automatically preparing the gun for the next shot. Such guns have proven to be very popular, especially for firing paintballs, probably because their simplicity makes them relatively economical to build and operate.
When such a gun is fired, various functions relating to loading must be performed before another projectile can be propelled from the gun. One common prior art design in such guns is to provide a bolt in a longitudinally translating configuration constrained to move with the hammer. Two functions performed by such a gun bolt include (a) opening a gun loading port to permit the next projectile in succession to be fired to enter into the breech of the gun, and (b) closing the loading port and chambering the projectile, that is, moving the projectile forward from the breech into the firing chamber of the gun so it is properly positioned and ready for receipt of propulsion gas. Because the hammer in such a gun design is held rearward in the cocked position when the gun is ready to fire, the bolt has not yet performed function of closing the loading port and chambering the projectile. Hence the gun is said to fire from an xe2x80x9copen boltxe2x80x9d.
As an open bolt gun is fired, the bolt moves forward with the hammer to close the loading port and chamber the projectile. Generally the projectile enters the loading port just as the gas released for propulsion reaches its rear surface. In such open bolt designs, the hammer performs two very different functions. First, it provides the impact function to open a valve to release compressed gas as the gun is fired. Second, it serves to receive the motive force of the gas released for recocking, and in response thereto, move the associated gun components to perform the recocking function.
A pneumatic gun can also be provided that fires from a closed rather than an open bolt. That is, the bolt closes the loading port and chambers the new projectile as part of the recocking process of preparing the gun to be fired again, rather than as the first part of the firing operation that occurs after the trigger is pulled. Generally in prior art closed-bolt guns, the hammer is required to perform only the valve impacting function. In such prior art guns, other mechanisms are provided to move the bolt, and, in some cases, to recock the hammer.
Firing with a closed bolt is potentially beneficial for several reasons. Since the bolt does not travel with the hammer when the hammer moves (toward the valve) upon firing, fewer components are subject to sliding friction. Consequently, variations in hammer velocity resulting from friction acting on bolt components is eliminated. Thus, the impact force of the hammer on the valve is more repeatable, and the amount of gas released is more consistent, resulting in more uniform projectile velocity, and hence better projectile accuracy.
Some guns, such as pellet guns (which typically are intended to provide extremely high accuracy), would benefit from a shorter firing interval that is made possible in a closed-bolt gun. In a closed-bolt gun, the hammer spring no longer must provide energy for closing the loading port and chambering the projectile, since such tasks are completed during the recocking process. Consequently xe2x80x9clock-timexe2x80x9d, i.e., the time elapsed between the time of pulling the trigger and the time when the valve releases compressed gas, can be made shorter. Since there is less time for the gun to move off target between the pulling of the trigger and the exiting of the pellet from the barrel, the gun accuracy is improved. Also, as such a gun is fired, there is less moving mass within the gun that might disturb the shooter""s aim.
Paintball guns would also benefit from the way the paintball is chambered in a closed-bolt gun. It has been observed that a paintball may start rolling as it is being pushed forward by the bolt from the breech to the firing chamber. If the propulsion gas is released to push against the paintball before the paintball has completely come to a stop, as will be more likely in an open-bolt than in a closed-bolt gun, the rolling motion can increase the chance of imparting a spin to the paintball that can upset its trajectory during flight.
Unfortunately, the mechanisms heretofore available to provide closed bolt pneumatic gun operation are generally more complex (and hence more expensive and troublesome to maintain), than typical open-bolt gun mechanisms. Hence, a significant and as yet unmet need exists for a semiautomatic pneumatic gun that is comparable in simplicity to open bolt gun designs, but that provides better gun performance by firing with a closed bolt.